In general, a heat exchanger refers to a device in which an interior refrigerant passage is formed so that refrigerant exchanges heat with external air while being circulated through the refrigerant passage. The heat exchanger is used in various air conditioning devices, and is employed in various forms such as a fin tube type, a serpentine type, a drawn cup type and a parallel flow type according to various conditions in which it is used.
The heat exchanger has an evaporator-using refrigerant as heat exchange medium, which is divided into one-, two- and four-tank types:
In the one-tank type heat exchanger, tubes formed by coupling one-tank plate pairs each having a pair of cups formed at one end and a U-shaped channel defined by an inside separator are laminated alternately with heat radiation fins.
In the two-tank type heat exchanger, tubes formed by coupling two-tank plate pairs each having cups formed at the top and bottom are laminated alternately with heat radiation fins.
In the four-tank type heat exchanger, tubes formed by coupling four-tank plate pairs each having cup pairs formed at the top and bottom and two channels divided by a separator are laminated alternately with heat radiation fins.
Describing hereinafter in more detail with reference to FIGS. 1 to 3, the one-tank type heat exchanger includes a pair of parallel tanks 40 placed at the top of the exchanger and having parallel cups 14 and holes 14a formed in the cups 14, tubes 10 each formed by welding two single or double head plates 11 having a predetermined length of separators 13 extended from between the pair of tanks 40 to define a generally U-shaped channels 12 in which the tanks 40 are coupled together at both sides of the each tube 10, heat radiation fins 50 laminated between the tubes 10 and two end plates 30 provided at the outermost sides of the tubes 10 and heat radiation fins 50 to reinforce the same.
In each tube 10, both plates are embossed to have a number of inward-projected first beads 15 so that a turbulent flow is formed in refrigerant flowing through the channel 12.
Further, in the each tube 10, the channel 12 has refrigerant distributing sections 16 in inlet and outlet sides thereof, in which each refrigerant distributing section 16 has a plurality of paths 16b partitioned by at least one second beads 16a so that refrigerant is uniformly distributed into the channel 12.
In addition, since the double head plate is substantially same as the single head plate 11 except that one or two cups are provided in the bottom end of the double head plate, hereinafter only the single head plate 11 having two cups 14 formed in the top end will be illustrated for the sake of convenience.
The tubes 10 also include manifold tubes 20 projected into the tanks 40 to communicate with the inside of the tanks 40, in which one of the manifold tubes 20 has an inlet manifold 21 connected to an inlet pipe 2 for introducing refrigerant and the other one of the manifold tubes 20 has an outlet manifold 21 connected with an outlet pipe 3 for discharging refrigerant.
The tanks 40 having the inlet and outlet manifolds 21 are provided with partition means 60 for separating inflow refrigerant from outflow refrigerant in the refrigerant flow within the evaporator 1 as shown in FIG. 1.
As a consequence, the tanks 40 are classified into “A” part, “B” part for receiving refrigerant U-turned from the A part, “C” part communicating with the B part for receiving refrigerant, and “D” part for receiving refrigerant U-turned from the C part and then discharging the same to the outside.
When being introduced through the inlet side manifold 21, refrigerant is uniformly distributed in the A part of the tank 40 and flows through the U-shaped channels 12. In succession, refrigerant is introduced into the B part of an adjacent tank 40, and then flows into the C part of the same tank 40 through the U-shaped channels 12 of the tubes 10 and 20. Finally, refrigerant is introduced into the D part of the tank 40 having the outlet side manifold 21 to be discharged to the outside.
Through the heat exchange with the air blown between the tubes 10 and 20, the evaporator 1 as above evaporates refrigerant circulating along refrigerant lines of a cooling system while sucking and discharging the same so as to cool the air blown indoors via evaporation latent heat.
However, as shown in FIG. 3, the first beads 15 in the plates 11 are formed circularly so that stagnation points occur in the inflow direction of the first beads 15 when refrigerant is introduced and large pressure is applied to the stagnation points, thereby increasing the pressure drop of refrigerant. Also, refrigerant flowing through the channel 12 is crowded in the periphery having ununiform flow distribution.
Regarding that the evaporator 1 is being gradually miniaturized into a compact size, when the pressure drop of refrigerant is increased to impart ununiform flow distribution to refrigerant, the evaporator 1 is to have overcooled/overheated sections. In the overcooled section, a problem of icing may occur in the surface of the evaporator. In the overheated section, the temperature variation of air degrades the performance of the air conditioning system thereby causing unstableness to the air conditioning system. This also increases the temperature distribution variation of the air passing through the evaporator thereby to degrade the cooling performance.